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Feb. 22, 2012 -- An experimental blood test for Parkinson's disease is more than 90% accurate in diagnosing the progressive disorder that affects movement and balance, according to its developers.

The test requires a single drop of blood, says Robert Nagele, PhD, a professor of medicine at the University of Medicine and Dentistry of New Jersey School of Osteopathic Medicine.

It looks for specific proteins that are produced by the body in response to Parkinson's disease, he tells WebMD.

Nagele is also the founder of Durin Technologies, the test developer. Another co-researcher is a paid consultant for the company.

No blood test is yet commercially available for Parkinson's, which affects 5 million people worldwide. The study is published in PLoS One.

The news was met with cautious optimism by two experts.

About Parkinson's

In Parkinson's, the nerve cells or neurons in a brain region responsible for muscle movement and coordination deteriorate over time. Normally these cells produce a chemical called dopamine. Dopamine helps regulate such bodily functions as movement.

"Parkinson's affects a specific part of the brain known as the substantia nigra," Nagele says. At least a third of the neurons in this area have already died before symptoms appear, he says.

Symptoms include shaking, tremor, slowness of movement, stiffness in the arms, legs, and trunk, and balance problems.

Doctors diagnose it by taking a medical history and doing a neurological exam.

A blood test could help doctors diagnose and treat the disease earlier. Many teams are working on such tests.

Blood Test for Parkinson's: Study Details

When brain cells die, Nagele says, they explode ''like a water balloon breaking."

The contents of those dying cells spill partially back into the blood. "Their debris is released and your body will sense it and develop autoantibodies to clear that debris," he says.

The new test looks for these autoantibodies in the blood specific to the disease. The researchers narrowed down a list of more than 100 of these autoantibodies to 10 that looked most promising. When these antibodies rise to a certain level, it signals disease, Nagele says.

To evaluate the Parkinson's test, Nagele's team looked at more than 150 blood samples, including:

Overall, the test identified 93% of those who had Parkinson's. It identified correctly 100% of those who did not have it. Both results are considered important.

It could tell the difference between blood samples from patients with Parkinson's, those with the other disorders, and those who were healthy.

Nagele estimates the test, when and if available, would cost about $200.

The new research is a ''proof of principle'' study, he says, and much more research is needed.

Blood Test for Parkinson's: Second Opinion

"It is very exciting to see that many groups around the world have been attempting to develop blood tests for Parkinson's disease," Michael Okun, MD, medical director of the National Parkinson Foundation, tells WebMD. He reviewed the results.

Although Okun calls the new study interesting, he says that ''it only included 29 patients."

However, he remains hopeful that the research will lead to a usable blood test.

"It sounds feasible and probably worth pursuing," says M. Flint Beal, MD, the Anne Parrish Titzell professor of neurology and neuroscience at the Weill Medical College of Cornell University. He also reviewed the findings. He is also developing an early blood test for Parkinson's disease that uses a different approach.

"This is something that should be validated," he says of the new test. "What frequently happens is, the test looks very good initially. When you expand it to a larger population, the accuracy falls off." Further study is needed, he says.